Update Node interface

[falsandtru]

TypeScript Version: 3.0.0-dev.201xxxxx

Search Terms:

Code

Expected behavior:

interface Node extends EventTarget {
    readonly childNodes: NodeListOf<Node & ChildNode>;
    readonly firstChild: Node & ChildNode | null;
    readonly lastChild: Node & ChildNode | null;
    readonly nextSibling: Node | null;
    readonly parentElement: Element | null;
    readonly parentNode: Node & ParentNode | null;

Actual behavior:

interface Node extends EventTarget {
    readonly childNodes: NodeListOf<Node & ChildNode>;
    readonly firstChild: Node | null;
    readonly lastChild: Node | null;
    readonly nextSibling: Node | null;
    readonly parentElement: HTMLElement | null;
    readonly parentNode: Node | null;

Playground Link:

Related Issues:
#4689

[mhegazy]

PRs welcomed. You can find more information about contributing lib.d.ts fixes at https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes.